1997 OBD 7.3 Diesel SYStem Operation

8/3/2019 1997 OBD 7.3 Diesel SYStem Operation

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FORD MOTOR COMPANY REVISION DATE: APRIL 1, 2003 PAGE 1 OF 25

1997 MY OBD System Operation

Summary for 7.3L Diesel Engine

Table of Contents

Introduction – OBD-I and OBD-II .......................................................................2 OBD-II Systems...................................................................................................2 OBD-I Systems....................................................................................................2 Misfire Monitor.....................................................................................................3 Low Data Rate System.......................................................................................3 Misfire Algorithm Processing ..............................................................................3 Glow Plug Monitor...............................................................................................4 Comprehensive Component Monitor - Engine .................................................7 Engine Inputs (Analog)........................................................................................7 Engine Inputs (Digital).......................................................................................16 Engine Outputs..................................................................................................17 Comprehensive Component Monitor - Transmission ....................................19

General ..............................................................................................................19 Transmission Inputs..........................................................................................19 Transmission Outputs.......................................................................................22 4R100 (E4OD) (RWD) Transmission..............................................................25




Int roduc t ion – OBD-I and OBD-II

OBD-II Systems

California OBD-II applies to all gasoline engine vehicles up to 14,000 lbs. Gross Vehicle Weight Rating (GVWR)starting in the 1996 MY and all diesel engine vehicles up to 14,000 lbs. GVWR starting in the 1997 MY.

"Green States" are states in the Northeast that chose to adopt California emission regulations, starting in the 1998MY. At this time, Massachusetts, New York, Vermont and Maine are Green States. Massachusetts and Mainereceive California – certified vehicles for passenger cars and light trucks up to 14,000 lbs. GVWR. New York andVermont receive California – certified vehicles for passenger cars and light trucks up to 6,000 lbs. GVWR.

The National LEV program (NLEV) requires compliance with California OBD-II, including 0.020" evaporativesystem monitoring requirements. The NLEV program applies to passenger cars and light trucks up to 6,000 lbs.GVWR nation-wide from 2001 MY through 2003 MY

Federal OBD applies to all gasoline engine vehicles up to 8,500 lbs. GVWR starting in the 1996 MY and all dieselengine vehicles up to 8,500 lbs. GVWR starting in the 1997 MY.

OBD-II system implementation and operation is described in the remainder of this document.

OBD-I Systems

If a vehicle is not required to comply with OBD-II requirements, it utilizes an OBD-I system. OBD-I systems areused on all over 8,500 lbs. GVWR Federal truck calibrations. Federal > 8,500 lbs. OBD-I vehicles use the samePCM, J1850 serial data communication link, J1962 Data Link Connector, and PCM software as the correspondingOBD-II vehicle.

The following list indicates what monitors and functions have been altered for OBD-I calibrations:

Monitor / Feature Calibration

ComprehensiveComponent Monitor

All circuit checks same as OBD-II. Some rationality and functional tests are calibratedout. MIL control for Federal truck applications is unique, not consistent with OBD-II MILillumination.

Glow Plug Monitor Glow Plug diagnostics do not set the MIL on Federal truck applications over 8,500lbs.

CommunicationProtocol and DLC

Same as OBD-II, all generic and enhanced scan tool modes work the same as OBD-IIbut reflect the OBD-I calibration that contains fewer supported monitors. "OBDSupported" PID indicates OBD-I.

MIL Control Illuminates the MIL for P0117 and P0118 (ECT), P0197 and P0198 (EOT), P0237 andP0238 (MAP), P2285 and P2286 (ICP), P1148 and P1149 (Boost hose), P0122 andP0123 (Pedal position)




Misfire Monitor

Low Data Rate System

The LDR Misfire Monitor utilizes a low-data-rate Hall Effect camshaft position (CAMP) sensor signal triggered off a24-tooth camshaft-timing wheel. One narrow window and an opposing wide window provide sync pulses to the

CAMP sensor to indicate camshaft position for correct cylinder timing. The PCM calculates camshaft rotationalvelocity for each cylinder from this position signal. The acceleration for each cylinder is then calculated into a

percentage delta change decrease in velocity for use by the misfire algorithm. The resulting deviant cylinderacceleration values are used in evaluating misfire.

Misfire is defined as a loss of compression. The amount of compression loss in a cylinder that misfire monitor willdetect is referenced as a 3/16" or larger hole in a cylinder or valve train component.

Misfire Algorithm Processing

The acceleration that a piston undergoes during a normal firing event is directly related to the amount of torque thata cylinder produces. For misfire determination the CAMP signal is processed at the peak instantaneous inverse

velocity angle of 90o

after top dead center (ATDC) from the previous cylinder-firing event. The calculated inverse

velocity of a cylinder under test is compared to the previous cylinder-firing event to establish a percentage deltavelocity change decrease. A cylinder with a misfire is identified by a large delta velocity value. When the delta value

exceeds the calibrated threshold, the misfire algorithm increments the specific cylinders misfire counter.

The numbers of misfires are counted in a block of 1000 revs. (The misfire counters are not reset if the misfiremonitor is temporarily disabled such as an off idle condition, etc.)

To insure accurate misfire calculation and reliable cylinder misfire quantification, misfire data is sampled at enginespeeds below 750 RPM. Misfire data becomes unreliable in an operating range outside of the idle region. For this

reason other engine operating parameters are monitored to insure misfire operates in a region that yields accuratemisfire results. The following table outlines the entry conditions required in order to execute the misfire monitor

algorithm.




Glow Plug Monitor

Glow Plug Control, Comprehensive Component Monitors, and Wait to Start Indicator—California

The California glow plug system is composed of a glow plug relay, glow plug shunt strips, shunt strip monitorcircuits, glow plugs, glow plug light, and the associated wiring harness. The glow plug on-time is controlled by the

Powertrain Control Module (PCM) and is a function of oil temperature, barometric pressure and battery voltage.The PCM enables the Glow Plug Relay, which drives the shunt sense strips, which in turn drive the individual glow

plugs. Glow plug on-time normally varies between 1 and 120 seconds. The power to the glow plugs is providedthrough the Glow Plug Relay directly from the vehicle battery. The PCM monitors through two shunt monitoring

circuits, one per bank, and detects glow plug functionality.

Glow Plug Relay Control Circuit Check:

DTCs P0380 – Glow Plug Relay Circuit Check

Monitor execution Continuous (Background 25ms – 50ms)

Monitor Sequence None

Sensors OK Not Applicable

Typical Monitoring Duration Internal to Chip.

Typical Glow Plug Module Control Circuit Check Entry Conditions:

No Entry Conditions

Typical Glow Plug Module Control Circuit Check Malfunction Thresholds:

Internal to chip checks for open circuit, short to ground, and short to power.




Glow Plug Monitor Operation:

DTCs P1391 – Glow Plug Bank 1 Failure

P1393 – Glow Plug Bank 2 Failure

P1395 – Absolute Voltage Drop Across Bank # 1

P1396 – Absolute Voltage Drop Across Bank # 2

Monitor execution P1391 – Continuous

P1393 – Continuous

P1395 – During the absolute test

P1396 – During the absolute test


Sensors OK Not Applicable

Monitoring Duration P1395 – Greater than 30 seconds.

P1396 – Greater than 30 seconds.

Typical Glow Plug Monitor Entry Conditions:

P1391 – Battery Voltage (IVPWR) is between 11.5 and 14 Volts and Glow Plug Duty Cycle is 100%.

P1393 – Battery Voltage (IVPWR) is between 11.5 and 14 Volts and Glow Plug Duty Cycle is 100%. P1395 – Battery Voltage (IVPWR) is between 11.5 and 14 Volts, Glow Plug Duty Cycle is 100%, and GlowPlug on time is greater than 30.5 seconds.

P1396 – Battery Voltage (IVPWR) is between 11.5 and 14 Volts, Glow Plug Duty Cycle is 100%, and GlowPlug on time is greater than 30.5 seconds.

Typical Glow Plug Monitor Malfunction Thresholds:

P1391 – When the Bank #1 shunt signal is lower than a specified value (.66 volts) the fault is set.P1393 – When the Bank #2 shunt signal is lower than a specified value (.66 volts) the fault is set.

P1395 – During the absolute test a fault is set if the voltage drops below a specified value (155 A/D counts)

on Bank #1.

P1396 – During the absolute test a fault is set if the voltage drops below a specified value (155 A/D counts)

on Bank #2.




Glow Plug Wait to Start Light Operation:

DTCs P0381 – Glow Plug indicator circuit malfunction

Monitor execution Continuous (Background 25ms-50ms)


Sensors OK Not applicable

Typical Monitoring Duration Internal to Chip

Glow Plug Light Wait to Start Light Entry Conditions:

Glow Plugs Enabled

Glow Plug Light Wait to Start Light Malfunction Thresholds:

Status internal to chip




Comprehensive Component Monit or - Engine

Engine Input s (Analog)

Battery Voltage (IVPWR):

DTCs P0562 - System Voltage Low




Typical Monitoring Duration Less than 2 second

Typical Battery Voltage Entry Conditions:

No entry conditions.

Typical Battery Voltage Malfunction Thresholds:

Voltage less 6.51 V.

Barometric Pressure (BP) Sensor Circuit Check:

DTCs P0107 - Barometric pressure sensor circuit low input

P0108 – Barometric pressure sensor circuit high input





Typical Barometric Pressure Sensor Circuit Check Entry Conditions:

No entry conditions.

Typical Barometric Pressure Sensor Circuit Check Malfunction Thresholds:

P0107 – Voltage less than 0.04 volts.

P0108 – Voltage greater than 4.90 volts.




Manifold Absolute Pressure (MAP) Sensor Circuit Check:

DTCs P0237 - Turbo boost sensor A circuit low input

P0238 – Turboboost sensor A circuit high input





Typical Manifold Absolute Pressure Sensor Circuit Check Entry Conditions:

No Entry Conditions

Typical Manifold Absolute Pressure Sensor Circuit Check Malfunction Thresholds:

P0237 – Frequency less than 4500Hz

P0238 – Frequency greater than 13000Hz




Manifold Absolute Pressure Functional Check Operation:

DTCs P0236 – Turbo boost sensor A circuit performance

P1247 – Turbo boost pressure low

P1248 – Turbo boost pressure not detected



Sensors OK P0236 – Manifold Absolute Pressure (MAP), Barometric Pressure (BP)

P1247 – Manifold Absolute Pressure (MAP), Barometric Pressure (BP)

P1248 – Manifold Absolute Pressure (MAP), Barometric Pressure (BP)

Typical Monitoring Duration P0236 – Greater than 10 seconds

P1247 – Greater than 10 seconds

P1248 – Greater than 15 seconds

Typical Manifold Absolute Pressure Functional Check Entry Conditions:

P0236 – Mass Fueling Desired (MFDES) < 14 mg/stroke and Engine Speed (N) < 850 rpm

P1247 – No Entry Conditions.

P1248 – No Entry Conditions.

Typical Manifold Absolute Pressure Functional Malfunction Thresholds:

P0236 – Fault sets if Manifold Absolute Pressure (MAP) signal is higher than the specified pressure. (MAP >

70 kPa, Manifold Gauge Pressure (MGP) > 30 kPa)

P1247 – Fault sets if a minimum specified boost doesn't occur. (F-Series: Engine Speed(N)>1750rpm,

Volume Fuel Desired (VFDES) >40, Manifold Absolute Pressure (MAP) chg<30 kPa - E-Series: N>2600,

VFDES>30, MAP chg<8 kPa)

P1248 – Fault sets if a minimum specified boost doesn't occur. (Engine Speed (N) > 1500rpm, Volume FuelDesired (VFDES) > 32, Manifold Absolute Pressure (MAP) chg<5 kPa)




Exhaust Back Pressure (EBP) Sensor Circuit Check:

DTCs P0472 - Exhaust pressure sensor circuit low input

P0473 – Exhaust pressure sensor circuit high input



Sensors OK Not applicableTypical Monitoring Duration Less than 1 second

Typical Exhaust Back Pressure Sensor Circuit Check Entry Conditions:

No Entry Conditions

Typical Exhaust Back Pressure Sensor Circuit Check Malfunction Thresholds:



Exhaust Back Pressure Functional Check Operation:

DTCs P0471 - Exhaust press sensor circuit performance

P0478 – Exhaust press control valve high input


Monitor Sequence None.

Sensors OK Exhaust Back Pressure (EBP)

Typical Monitoring Duration P0471 – Greater than 3 seconds.


Typical Exhaust Back Pressure Functional Check Entry Conditions:

P0471 - Engine speed (N) is greater than 2300 RPM.

P0478 - Engine speed (N) is greater than 650 RPM.

Typical Exhaust Back Pressure Functional Thresholds:

P0471 - Checks for a minimum change in Exhaust Back Pressure (EBP) (20kPaG).

P0478 - Checks the Exhaust Back Pressure sensor (EBP) by looking for a pressure above a specified value

for the sensor (240kPaG).




Engine Oil Temperature (EOT) Sensor Circuit Check:

DTCs P0197 - Engine oil temp sensor circuit low input

P0198 – Engine oil temp sensor circuit high input





Typical Engine Oil Temperature Sensor Circuit Check Entry Conditions:

No Entry Conditions

Typical Engine Oil Temperature Sensor Circuit Check Malfunction Thresholds:

P0197 – Voltage less than .15.

P0198 – Voltage greater than 4.80.

Intake Air Temperature (IAT) Sensor Circuit Check:

DTCs P0112 – Intake air temp sensor circuit low input

P0113 – Intake air temp sensor circuit high input




Typical Intake Air Temperature Entry Conditions:

No Entry Conditions.

Typical Intake Air Temperature Sensor Circuit Check Malfunction Thresholds:






Injection Control Pressure (ICP) Sensor Circuit Check:

DTCs P1280 - ICP circuit out of range low

P1281 – ICP circuit out of range high




Typical Injection Control Pressure Sensor Circuit Check Entry Conditions:

No Entry Conditions

Typical Injection Control Pressure Sensor Circuit Check Malfunction Thresholds:






Injection Control Pressure Functional Check Operation:

DTCs P1209 – ICP system fault

P1210 – ICP above expected level

P1211 – ICP pressure above/below desired

P1282 – Excessive ICP pressure

Monitor execution Continuous


Sensors OK Injection Control Pressure (ICP)

Typical Monitoring Duration P1209 – Greater than 5 seconds.



P1282 – Greater than 1.5 seconds.

Typical Injection Control Pressure Functional Check Entry Conditions:

P1209 – The engine is running (mode = 2)

P1210 – The engine is off (mode =0), the engine speed is 0.

P1211 – The engine is running (mode =2)

P1282 – The engine is running (mode =2)

Typical Injection Control Pressure Functional Malfunction Thresholds:

P1209 – Fault sets when the difference between the commanded and actual Injection Control Pressure (ICP)exceeds a specified value (12 MPa).

P1210 – When the actual pressure is greater than a specified maximum pressure (8 MPa)

P1211 – Fault sets when actual pressure differs from the commanded by a specified value (+2.0 MPa or –

2.8 MPa)

P1282 – When the actual pressure is greater than a specified maximum pressure (25 MPa)




Pedal Position Sensor Circuit Check:

DTCs P0122 – Accelerator pedal sensor circuit low input

P0123 – Accelerator pedal sensor circuit high input




Typical Pedal Sensor Circuit Check Entry Conditions:

Pedal not at idle position. (IVS = 1)

Typical Pedal Sensor Circuit Check Malfunction Thresholds:

P0122 – Less than .37 V.

P0123 – Greater than 4.5 V.

Note: Pedal position sensor faults illuminate the MIL to inform the customer of the malfunction. The vehicle cannotbe driven because the engine remains at idle. Engine emissions are not affected.

Idle Validation Switch (IVS) Sensor Circuit Check:

DTCs P0221 – Throttle switch B circuit malfunction





Typical Idle Validation Switch (IVS) Sensor Circuit Check Entry Conditions:

Pedal at idle position. (IVS = 0)

Typical Idle Validation Switch (IVS) Sensor Circuit Check Malfunction Thresholds:

Greater than 1.60 volts or less than .40 volts.




Fuel Level Input Operation:

DTCs P0460 – Fuel Level Sensor Circuit Malfunction




Typical Monitoring Duration Greater than 33 seconds.

Fuel Level Input Entry Conditions:

No entry conditions

Fuel Level Input Malfunction Thresholds:

Instrument cluster driver chip checks for open circuit, or short circuit.




Engine Inputs (Digital)

Camshaft Position Sensor (CMP) Check Operation:

DTCs P0341 –Camshaft position sensor ckt performance

P0344 – Camshaft position sensor ckt intermittent




Typical Monitoring Duration P0344 – Greater than .25 seconds.

Typical Camshaft Position Sensor Malfunction Entry Conditions:

P0341 – No Entry Conditions

P0344 – Engine Speed (N) is greater than 500 rpm.

Typical Camshaft Position Sensor Malfunction Thresholds:

P0341 – If time since last CAMP signal is too short (<15 clock counts), and this occurs 255 times during onekey-on cycle the fault is set.

P0344 – Fault sets when the synchronization tooth signal is not detected when expected.

Injector Driver Module (IDM) Check Operation:

DTCs P1316 –Injector circuit/IDM codes detected

P1670 – Engine Feedback (EF) signal not detected





Typical Injector Driver Module (IDM) Malfunction Entry Conditions:

P1316 – No Entry Conditions

P1670 – Engine is running (mode=2).

Typical Injector Driver Module (IDM) Malfunction Thresholds:

P1316 – The PCM interrogates the Injector Driver Module (IDM) for a 300 µsec, 400 µsec, or 500 µsecextension on the Engine Feedback line. If any of these extensions exist that indicates that the Injector DriverModule (IDM) has stored codes then the fault is set.

P1670 – When a commanded Injector Driver Module (IDM) response is not received this fault is set.




Engine Outputs

Dual Alternator Control Check Operation:

DTCs P1107 – Dual alternator lower circuit malf. (control)





Typical Dual Alternator Control Entry Conditions:

No entry conditions

Typical Dual Alternator Control Malfunction Thresholds:

Actuator driver status indicates open/short

Exhaust Pressure Regulator (EPR) Valve Check Operation:

DTCs P0475 – Exhaust press control valve malfunction





Exhaust Pressure Regulator (EPR) Valve Check Entry Conditions:

No entry conditions

Exhaust Pressure Regulator (EPR) Valve Check Malfunction thresholds:

Actuator driver status indicates open/short




Fuel Pump Monitor Operation:

DTCs P0231 – Fuel Pump circuit failure




Typical Monitoring Duration Greater than 1 second.

Fuel Pump Monitor Malfunction Entry Conditions:

Fuel Pump commanded "on", engine not cranking, Battery Voltage (IVPWR) above 11V

Fuel Pump Monitor Malfunction Thresholds:

When the fuel pump monitor sees a voltage other than expected for a specified time after the fuel pump iscommanded "on", the fault is set.




Comprehensive Component Monitor - Transmission

General

The MIL is illuminated for all emissions related electrical component malfunctions. For malfunctions attributable toa mechanical component (such as a clutch, gear, band, valve, etc.), some transmissions are capable of not

commanding the mechanically failed component and providing the remaining maximum functionality (functionalityis reassessed on each power up)- in such case a non-MIL Diagnostic Trouble Code (DTC) will be stored and, if

so equipped, a Transmission Control Indicator Light (TCIL) will flash.

Transmission Inputs

Transmission Range Sensor Check Operation:

DTCs P0708, P0705 (open/invalid pattern for digital TRS)



Sensors OK

Monitoring Duration 30 seconds

Typical TRS check entry conditions:

Auto Transmission Entry Conditions Minimum Maximum

Gear selector position each position for up to 30 seconds 480 seconds

Typical TRS malfunction thresholds:

For digital sensor: Invalid pattern from 3 or 5 digital inputs and/or 1 analog circuit open for 5 seconds




Vehicle Speed Sensor Functional Check Operation:

DTCs P0500



Sensors OK

Monitoring Duration 30 seconds

Typical VSS functional check entry conditions:


Gear selector position drive

Engine rpm (above converter stall speed) OR 3000 rpm

Turbine shaft rpm (if available) OR 1500 rpm

Output shaft rpm 650 rpm

Vehicle speed (if available) 15 mph

Manual Transmission Entry Conditions

Engine load 50 %

Engine rpm 2400 rpm

Typical VSS functional check malfunction thresholds:

Vehicle is inferred to be moving with positive driving torque and VSS is < 1 - 5 mph for 5 seconds




Transmission Fluid Temperature Sensor Functional Check Operation:

DTCs (non-MIL) P0712, P0713 (open/short)

P1713, (stuck low), P1718 (stuck high)

Monitor execution continuous

Monitor Sequence none

Sensors OK (ECT substituted if TFT has malfunction)Monitoring Duration 5 seconds for electrical, 600 seconds for functional check

Typical TFT functional check entry conditions:


Engine Coolant Temp (hot or cold, not midrange) > 100oF < 20

oF

Time in run mode 500 sec

Time in gear, vehicle moving, positive torque 150 sec

Time with engine off (soak time) 420 min

Vehicle Speed 15 mph

Typical TFT malfunction thresholds:

Electrical check:

TFT voltage <0.05 or > 4.6 volts for 5 seconds

TFT functional check (TFT stuck at high temperature or stuck at low temperature):

< 6oF rise or fall in TFT after startup




Transmission Outputs

Shift Solenoid Check Operation:

DTCs SS A - P0750 electrical,

P1714 ISIG functional

SS B - P0755 electrical,

P1715 ISIG functional

Monitor execution electrical - continuous, functional - during off to on solenoid transitions


Sensors OK

Monitoring Duration 10 solenoid events

Typical Shift Solenoid ISIG functional check entry conditions:

Entry Conditions Minimum Maximum

Transmission Fluid Temp 70oF 225

oF

Throttle position positive drive torque (actual TP

varies)

Typical Shift Solenoid mechanical functional check entry conditions:

Entry Conditions (with turbine speed) Minimum Maximum

Gear ratio calculated each gear

Throttle position positive drive torque

Typical Shift Solenoid mechanical functional check entry conditions:

Entry Conditions (without turbine speed) Minimum Maximum

Rpm drop is obtained each shift

Throttle position positive drive torque

Typical SS malfunction thresholds:

Electrical check: Output driver feedback circuit does not match commanded driver state for 5 seconds

ISIG functional check: ISIG chip hardware circuit does not detect characteristic current dip and rise produced

by solenoid movement.




Torque Converter Clutch Check Operation:

DTCs P0743 electrical,

P1740 ISIG functional, or P1744 mechanical functional

Monitor execution electrical - continuous,

mechanical - during lockup


Sensors OK VSS

Monitoring Duration 5 lock-up events

Typical Torque Converter Clutch ISIG functional check entry conditions:



oF

Engine Torque positive drive torque

Commanded TCC dutycycle for 0 rpm slip 60% 90%

Typical Torque Converter Clutch mechanical functional check entry conditions:


Throttle Position steady

Engine Torque positive drive torque


oF

Commanded TCC dutycycle (0 rpm slip) 60% 100%

Not shifting

Typical TCC malfunction thresholds:

Electrical check:

Output driver feedback circuit does not match commanded driver state for 5 seconds(> 1.0 volt ifcommanded on, < 2.0 volts if commanded off.)

ISIG functional check:

ISIG chip hardware circuit does not detect characteristic current dip and rise produced by solenoidmovement.

Mechanical check:

Slip across torque converter > 100 rpm or (on some applications) speed ratio < 0.93

Mechanical check:

Slip across torque converter < 20 rpm with converter commanded off (some applications)




Electronic Pressure Control Check Operation:

DTCs P1747 electrical,



Sensors OK

Monitoring Duration 5 seconds,

Typical EPC malfunction thresholds:

Electrical check:

Current feedback circuit is less than commanded current for 5 seconds

Inductive Signature Chip Communication Check Operation:

DTCs P1636 loss of communication

Monitor execution off-to-on solenoid transitions


Sensors OK

Monitoring Duration < 100 solenoid events

Typical Inductive Signature Chip Communication Check entry conditions:



oF

Solenoid commanded off duration < 2 seconds

Typical Inductive Signature Communication Chip malfunction thresholds:

Checksum error, chip not responding



4R100 (E4OD) (RWD) Transmission

(no turbine speed sensor)

Transmission Inputs

The Digital Transmission Range (DTR) sensor provides a single analog and three digital inputs to the PCM. ThePCM decodes the inputs to determine the driver-selected gear position (Park, Rev, Neutral, OD, 2, 1). This input

device is checked for opens and invalid input patterns. (P0708, P0705)

The Vehicle Speed Sensor (VSS) is an analog input that is checked for rationality. If the engine rpm is above the

torque converter stall speed and engine load is high, it can be inferred that the vehicle must be moving. If there isinsufficient output from the VSS sensor, a malfunction is indicated (P0500).

Transmission Output s

Shift Solenoids

The Shift Solenoid (SSA and SSB) output circuits are checked for opens and shorts by the PCM by monitoring the

status of a feedback circuit from the output driver (P0750 SSA, P0755 SSB).

All vehicle applications will utilize an inductive signature circuit to monitor the shift solenoids functionally. The ISIGcircuit monitors the current signature of the shift solenoid as the solenoid is commanded on. A solenoid thatfunctions properly will show a characteristic decrease in current as the solenoid starts to move. If the solenoid is

malfunctioning, the current will not change (P1714 SS1, P1715 SS2). The ISIG test runs in conjunction with theother transmission functional tests.

Torque Converter Clutch

The Torque Converter Clutch (TCC) output circuit is either an on/off or duty-cycled output that is checked

electrically for opens and shorts internally in the PCM by monitoring the status of a feedback circuit from the outputdriver (P0743).

Vehicle applications with on/off output drivers will utilize an inductive signature circuit to monitor the torque

converter clutch functionality. The ISIG circuit monitors the current signature of the TCC solenoid as the solenoid iscommanded on. A solenoid the functions properly will show a characteristic decrease in current as the solenoidstarts to move. If the solenoid is malfunctioning, the current will not change (P1740). The ISIG test runs in

conjunction with the other transmission functional tests.

Vehicle applications that use duty-cycled output drivers utilize a rationality check for TCC operation. Actuation ofthe TCC on and off will result in a change of the calculated speed ratio under high engine load. If a speed ratio

delta does not occur, a malfunction is indicated (P1744).

Electronic Pressure Control

The EPC solenoid is a variable force solenoid that controls line pressure in the transmission. The EPC solenoidhas a feedback circuit in the PCM that monitors EPC current. If the current indicates a short to ground (lowpressure), engine torque may be reduced to prevent damage to the transmission. (P1747, PCA)

1997 OBD 7.3 Diesel SYStem Operation

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Transcript of 1997 OBD 7.3 Diesel SYStem Operation